Such bodies serve to filter diesel exhaust or for catalytic cleaning of exhaust from internal combustion engines and have a monolithic sintered body. The housing enables a connection to the exhaust system of the internal combustion engine. The mounting and fixation of the monolithic body in the housing is problematical, since the porous ceramic substance has only a limited mechanical strength. It is therefore not possible to exert rather large clamping forces on the body to accomplish its secure and firm mounting.
A further difficulty in the mounting results from the need to compensate for the relatively large cross section tolerances of the body which occur during the fabrication, as well as the differences in thermal expansion which occur as a result of different coefficients of thermal expansion of the body material and the metal housing.
In the special field of exhaust catalytic engineering for automobiles, there are basically three main designs of catalysts, namely, tube catalysts, housing catalysts, and wound catalysts. The present invention refers to wound catalysts.
In DE 102 57 651 A1 is described a winding method for a catalyst body, in which at first a metal plate or a metal strip is deformed. This metal strip, hereinafter generally called a blank, is bent into a cylinder, so that its two opposite end regions overlap. After a monolith coated with a catalytically active material, especially one in ceramic form, has been wrapped in a support mat, the combination of monolith and mounting mat, here called the body, is shoved into the winding of the housing envelope. This winding is then stretched so that it firmly surrounds the body in the required manner. The winding, stretched in this way into its end shape, forms a housing or in general a housing envelope of the catalyst housing and is tacked with spot welds for fixation to certain places. At the end face, entry and exit funnels are arranged, being designed according to requirements for fastening to an exhaust pipe. The fastening of the entry and exit funnels is done each time by means of a circular weld seam along the edges of the housing envelope. To accomplish an optimal sealing of the catalyst housing, the exterior edge of the winding or housing envelope is joined by means of a weld seam to the underlying portion of the winding or housing envelope, i.e., the overlap is welded shut.
In DE 10 2006 026 814 A1 is described a housing in which a metal sheet as the housing envelope is wound onto the two end sheets at the entry and exit end. The long thin sheet is wound in several layers on the end sheets and then joined to them. The thin sheet can be easily wound. The multiple layers produce an excellent noise suppression, so that such housings give off practically no mechanical vibrations. Furthermore, the multiple layers at the same time act as a labyrinth seal, so that a simple fixation of the outer end of the metal sheet is entirely adequate, such as by a few weld spots.
In WO 9914119 (A2) is described a device for closing a housing in which spacers with a special surface are arranged in the circumferential direction about the housing so that they are fitted to the surface of the housing. The spacers here are contained in a circular mat that is enclosed around the housing in the circumferential direction.
According to DE 601 07 267 T2, a housing is formed by sheet metal elements that are joined together in the axial direction by roll-seam welding.
In JP 08284656 A is described a housing consisting of two metal strips arranged one on the other, which are partly overlapping in the circumferential direction.